The present inventive concept relates to an operation test of an integrated circuit (IC) chip, and more particularly, to an external loopback test in a transmitter-only IC chip.
Recently, operating frequencies of semiconductor ICs having a transceiver or transmitter function have dramatically increased due to a demand for a high speed multimedia system. These semiconductor ICs may be subjected to a loopback test before product shipment in order to test operating performance.
The loopback test is known as the most effective test method to verify physical layer (PHY) intellectual property (IP) in a serial interface, and is largely classified as an internal loopback test or an external loopback test.
In transceiver PHY having both transmit (TX) and receive (RX) capability, such as serial advanced technology attachment (SATA) or peripheral component interconnect express (PCIe) protocols, external loopback is possible during an at-speed test. However, since there is no receive pin for receiving signals from PHY with only TX, such as high-definition multimedia interface (HDMI) TX or low voltage differential signaling (LVDS) TX, external loopback is substantially impossible during an at-speed test.
In a case of PHY with only TX, if internal loopback is performed in a transmitter-only IC chip, it is completed based on a pre-driver stage without transmitting a signal to the exterior. Accordingly, an AC attribute test for final stage drivers connected to a transmit pad is not performed.
Therefore, conventionally, in order to perform an external loopback test in a transmitter-only IC chip, an additional receive pin and a separate RX unit for a test should be designed and mounted in a chip, or expensive high-speed test equipment is required for a test. However, the above methods increase IC size and manufacturing cost. Moreover, cost for an IC test is also increased.
As another method, golden RX is inserted on a test board of a tester to perform an external loopback test, but the test board becomes complex, and cost for setting and managing the golden RX is increased. In addition, since overkills or issues for each test may occur, depending on quality of the golden RX, a golden TX having controllability of an adequate level is required. Moreover, in a case of a test using the golden RX, test setup becomes relatively complex and thus test cost is increased also.